The coming year will test the validity of and alter if necessary the Liebman-Pugh model of visual receptor phosphodiesterase (PDE) control through kinetically resolved ATP and GTP 32P labelling experiments and via reconstitution using known stoichiometries of the active rhodopsin, GTP binding protein, GTP'ase, PDE oligomer subunits and opsin kinase. The pH kinetic method will be extended to study cyclic nucleotide and PDE control of cones. A battery of enzymatic functional tests will be applied to the rods of dystrophic retinas to try to learn kinetically what is missing in this defect of inbred mice and dogs.